1. Field of the Invention
The present invention relates to a thin film transistor-liquid crystal display (TFT-LCD). Specifically, it relates to a shorting bar for a TFT-LCD where the resistance of the even line shoreline bar and the odd line shorting bar is substantially similar in order to accurately test the TFT-LCD.
2. Discussion of Related Art
Generally, a TFT-LCD includes a bottom plate and a top plate. The bottom plate contains a plurality of pixel regions arranged in a matrix. Each pixel region includes a TFT switching element coupled to an associated pixel electrode. The top plate contains a common electrode and color filter, for displaying colors. A liquid crystal fills the space between the bottom and top plates. Additionally, polarizing plates, connected to both the bottom and top glass plates, polarize visible light rays.
The LCD uses shorting bars to test for poor panels during fabrication. In a conventional LCD the resistance of the shorting bars depends on the area occupied by them. Because even and odd lines are connected to shorting bars of different areas, it is difficult to test the electrical characteristic of an LCD accurately, and thus the detection of poor panels becomes difficult.
A conventional TFT-LCD shorting bar will be explained below with reference to the accompanying drawings. Referring to FIG. 1, a first shorting bar 1 connects to a plurality of odd lines 4 and even lines 5. A cutting region 6 is provided between the plurality of even lines 5 and first shorting bar 1, for separating the shorting bar. A semiconductor line 3 is formed perpendicular to the plurality of odd lines 4 and even lines 5. The semiconductor line 3 exists between first shorting bar 1 and pads associated with the plurality of even lines 5 and odd lines 4. Semiconductor line 3 and the plurality of even lines 5 include a second shorting bar 2. Second shorting bar 2 is connected to the source and drain regions of the plurality of even lines 5 through a chrome layer (not shown in FIG. 1).
A method of forming the plurality of odd lines 4 and shorting bar 1 of the conventional LCD will be explained below. As shown in FIG. 2A, aluminum is deposited on a transparent insulating substrate 10, and patterned to form a gate line 11. As shown in FIG. 2B, gate line 11 is coated with a photoresist that is patterned by exposure and development to overly a portion of gate line 11 corresponding to a pad.
Then, as shown in FIG. 2C, an anodizing oxide layer 12 is selectively formed on an exposed portion of gate line 11 using the photoresist pattern as a mask. After anodizing oxide layer 12 is formed, the photoresist pattern is removed. Next, a silicon nitride layer (SiNx) 13 is formed on the entire surface of substrate 10 including anodizing oxide layer 12. A conventional photolithography process is then carried out to selectively etch the silicon nitride layer using a patterned photoresist layer as a mask. As a result, only a portion of silicon nitride layer 13 remains on anodizing oxide layer 12. An amorphous silicon layer (a-Si:H) 14 is then formed on the overall surface of substrate 10 and selectively etched through photolithography process using a patterned photoresist. Accordingly, amorphous silicon layer 14 is left only on a predetermined portion of silicon nitride layer 13. Amorphous silicon layer 14 corresponds to a location between first shorting bar 1 and odd lines 4.
As shown in FIG. 2D, chrome layers 15a and 15b are formed on the entire surface of substrate 10 and selectively etched through photolithography process using a photoresist. The process forms a second shorting bar 15a and pad 15b. The design of the LCD places shorting bar 15a on a predetermined portion of amorphous silicon layer 14 and pad 15b on a predetermined pad region.
As shown in FIG. 2E, a passivation layer 16 is formed on the overall surface of the substrate and selectively removed, to thereby expose only pad 15b. Then, a conductive layer 17, such as ITO (Indium Tin Oxide), is formed on the entire surface of the substrate and selectively etched, such that only a portion remains on the pad region.
A method of forming the plurality of even lines 5 and second shorting bar 2 of the conventional LCD will be explained below. First of all, as shown in FIG. 3A, aluminum is deposited on transparent insulating layer 10 and patterned, to form gate line 11. As shown in FIG. 3B, a photoresist layer is coated on the entire surface of the substrate and selectively etched. As a result, a photoresist pattern is formed on both the pad region and cutting region 6, shown in FIG. 1.
As shown in FIG. 3C, anodizing oxide layer 12 is formed on an exposed portion of gate line 11 using the photoresist pattern as a mask, and then the photoresist pattern is removed. Silicon nitride layer 13 is formed on the overall surface of the substrate and selectively etched, leaving silicon nitride layer 13 only on anodizing oxide layer 12. Amorphous silicon layer 14 is formed and selectively etched to remain only on a predetermined portion of silicon nitride layer 13. Thus, amorphous silicon layer 14 is located between first shorting bar 1 and the pad region.
As shown in FIG. 3D, chrome layers 15a and 15b are formed on the overall surface of the substrate and patterned, to form a second shorting bar 15a and pad 15b on the pad region. Second shorting bar 15a and pad 15b are connected to each other. As shown in FIG. 3E, gate line 11 is selectively etched in order to form cutting region 6 (shown in FIG. 1). The conventional LCD design places cutting region 6 between first shorting bar 1 (shown in FIG. 1) and amorphous silicon layer 14 (shown in FIG. 3D). Passivation layer 16 is formed on the overall surface of the substrate and selectively etched in order to expose the pad region. A conductive layer 17, such as, for example, ITO, is formed on the overall surface of the substrate and selectively etched; thus, leaving conductive layer 17 only on pad 15b.
The aforementioned shorting bar of the conventional LCD has the following problem. Because the even line shorting bar is much thinner than the odd line shorting bar, the resistance of the even lines becomes larger than that of the odd lines. Accordingly, the IPT test to check the electrical characteristic of a picture of the LCD cannot be accurately carried out. As a result, it is difficult to detect a defective even line.